Propeller Pitch Calculator
Pitch ratio
66.7%
How it works
Propeller pitch and diameter determine thrust and efficiency for aircraft, drones, and RC boats. The Propeller Pitch Calculator computes theoretical pitch speed, advance ratio, and slip percentage from propeller dimensions and motor RPM.
**Pitch definition** Pitch is the theoretical distance the propeller advances through air in one full revolution (if air were a solid). A 10x4.7 propeller should advance 4.7 inches per revolution. At 10,000 RPM: theoretical pitch speed = 4.7 x 10,000 / 12 = 3,917 feet per minute = 44.5 mph. Actual speed is lower due to slip.
**Slip** Slip is the difference between theoretical pitch speed and actual aircraft speed, expressed as a percentage. Typical fixed-wing aircraft slip: 20 to 30% in cruise. Drones have higher effective slip due to hover efficiency characteristics.
**Diameter vs. pitch trade-off** Larger diameter: more thrust at low speed, higher torque load on motor, slower RPM needed. Higher pitch: more efficient at high speed but stalls at low speed, high current draw on climb/hover. For quadcopters: larger diameter, lower pitch props are more efficient at hover; smaller diameter, higher pitch props suit racing.
**Motor KV and propeller matching** Low KV motors (under 1,000 KV) pair with large diameter, low pitch props. High KV motors (2,300+ KV) pair with small diameter, higher pitch props. Mismatching causes motor saturation (high current, heat) or underwhelming thrust.
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Frequently Asked Questions
- Blade count is a trade-off between efficiency and thrust smoothness. 2-blade propellers: highest efficiency at a given diameter and RPM — each blade completes a full revolution with minimal interference from the other blade's wake. Best for low-drag, high-speed aircraft. 3-blade: better thrust at lower RPM (useful for wider bodies or when diameter is constrained), smoother (more power pulses per revolution), moderate efficiency reduction vs. 2-blade. 4-blade: smoothest vibration, highest thrust for a given diameter, lowest noise in many configurations — preferred when vibration causes fatigue or structural issues. For quadcopters: each motor has one propeller (typically 2-blade), so multi-blade tradeoffs are less relevant than for fixed-wing aircraft.
- Propeller efficiency is the ratio of useful thrust power output to shaft power input. A perfect propeller at its design airspeed would have 100% efficiency — real propellers achieve 75–88% efficiency at their design point, dropping at off-design speeds. Factors improving efficiency: operating at the design airspeed (props are optimized for one advance ratio), clean undamaged blades (nicks reduce efficiency significantly), correct pitch for the airspeed range, and appropriate diameter for the motor torque available. For fixed-pitch propellers on model aircraft: a prop optimized for climb will be inefficient at cruise, and vice versa. Variable-pitch props (rare in models) resolve this by adjusting pitch to the current airspeed.
- Static thrust (at zero forward speed, as in hover or launch) depends on propeller diameter, pitch, blade shape, and RPM. A rough formula for static thrust in grams: T = 4.392399 × 10^-8 × RPM^1.5 × (diameter in inches)^3.5 / pitch^0.5 × rho_ratio (air density correction, = 1 at sea level). Better approach: use measured thrust data from manufacturer or community databases (rcbenchmark.com, ecalc.ch). For quadcopters specifically: target a hover throttle of 50% (meaning the drone is lifting off at half throttle) — this corresponds to a thrust-to-weight ratio of 2:1, giving adequate responsiveness and efficiency. Higher T/W ratio (3:1) gives more performance but shorter flight time.
- KV (velocity constant) indicates RPM per volt with no load. With a battery: unloaded RPM = KV × voltage. Under load (with propeller), actual RPM is 70–85% of unloaded. Matching guidelines: Low KV (under 1,000): large diameter, low pitch props (10–14 inch diameter, 3–5 inch pitch). These motors produce high torque at low RPM — matches high-resistance large props. Medium KV (1,000–2,000): medium diameter, medium pitch (7–9 inch diameter, 4–6 pitch). Common for 450–550mm quadcopters. High KV (2,000–4,500): small diameter, higher pitch (4–6 inch diameter, 3–4 inch pitch). Racing applications, high-speed with small, fast-spinning props. Use ecalc.ch or similar thrust calculators to verify specific combinations before purchasing hardware.